Molecular cytogenetic findings in a four-way t(1;12;5;12)(p36;p13;q33;q24) underlying the ETV6-PDGFRB fusion gene in chronic myelomonocytic leukemia.

Fluorescence in situ hybridization (FISH) and reverse-transcription polymerase chain reaction (RT-PCR) detected the ETV6-PDGFRB fusion in a patient with chronic myelomonocytic leukemia characterized by bone marrow and peripheral blood eosinophilia and a four-way t(1;12;5;12)(p36;p13;q33;q24) on bone marrow cells. The patient consequently underwent imatinib mesylate therapy and achieved hematologic, FISH, and molecular remission. The FICTION technique (fluorescence immunophenotyping and interphase cytogenetics as a tool for the investigation of neoplasms) demonstrated that eosinophils and CD13(+) and CD14(+) cells belong to the neoplastic clone bearing the ETV6-PDGFRB rearrangement. Molecular cytogenetics is the most reliable approach to detect the involvement of promiscuous genes, such as PDGFRB, and to properly classify genetic entities for which targeted therapies are available. Assessment of cell lineages harboring the genomic lesion may contribute in the understanding of leukemogenic pathways.